Mechanism of Efficient Sediment Transport by Hyperconcentrated Flow in the Lower Yellow River (Part I)

The Yellow River, the second largest river in China, is well known as a highly sediment-laden river. The average annual sediment inflow entering the Lower Yellow River (Figure 1) is 1.6 billion tons. Every year, there are around 400 million tons of sediment deposit on the lower reach of the Yellow River, which results in raising of river bed with a speed of 10 cm per year. For decades, reduction of channel sedimentation has drawn attention of hydraulic engineers and geomorphologists (Xu, 2003). 

In the 1950, Soil-Water Conservation Project was initialized to control erosion in the Loess Plateau of the middle basin, which contributes 90% of the sediment loads. However, this project cannot completely solve the sediment problem, since there will be still 800 million tons of sediment yields annually after the project is finished (Qi and Li, 1996).  As early as the 1960s, the hyperconcentrated flow occurring on the Loess Plateau has been field investigated by hydraulic engineers. The research on hyperconcentrated flow of the Yellow River, which was originated by Dr. Ning Chien (Chien and Wan, 1999) in 1950’s, opens a new path by making full use of the channel for sediment transport. It has been evolved from pure theory into real engineering practices in recent years. 

Figure 1 Major Tributaries and Hydrologic Stations of Middle and Lower Yellow River in China

In the first International Workshop on Hyperconcentrated Flow held in Beijing in 1985, scientists from United States reported on the sediment transportation by lahars and hyperconcentrated flows at Mount St. Helens, Washington (Scott and Dinehart, 1985, Janda and Meyer, 1985, Pierson and Scott, 1985). Brown (1988) advanced the understanding of sediment transport of bed material discharged in sand bed channels through the developed theoretical concepts related to the effects of high concentration of suspended sediment of the water-sediment mixture along a 27-mile reach of the Cowlitz and Toutle Rivers in Washington. Julien and Lan (1991) used a physically based quadratic rheological model to test hyperconcentrated flows with experimental data. The model considers (1) cohesion between particles; (2) viscous friction between fluid and sediment particles; (3) impact of particles; and (4) turbulence. The resulting quadratic formulation of the shear stress was shown to be in excellent agreement with the experimental data sets. Rickenmann (1991) simulated fine-material slurry of a debris flow in a steep flume. The results showed that viscous effects became important below a limiting particle Reynolds number of about 10. Above this limiting value, density effects cause an increase in the bed-load transport rates as compared to similar conditions with clear water as transporting fluid.

In the book authored by Wang and Wan (1994), the rheological properties of hyperconcentrated flows were further revealed, as well as the mechanism of surface instability and drag reduction. Batalla et al. (1999) analyzed the hyperconcentrated flow occurred after collapse of a bridge in the Pyrenean Arás basin, Spain. The flood was characterized by transportation of large amounts of slope material, including debris flows. Along the main tributary, an intensive hyperconcentrated flow was observed during the rising stage, whereas in the main valley smaller flows occurred after failure of check dams. Lavigne and Suwa (2004) carried out observation of debris flows, hyperconcentrated flows, and stream flows in the Curah Lengkong River on the southeast slope of Mount Semeru in East Java, Indonesia. This study provided quantitative data for these flows in motion, and it also compared the data for different types of flow that occur in the same river. The influence of rainfall on debris flows, hyperconcentrated flows, and streamflow generation was also analyzed. A detailed case study in a small catchment on the Loess Plateau conducted by Hessel (2005) indicated that a number of corrections are necessary to be able to compare field measurements with results of soil erosion models: sediment volume should be subtracted from runoff volume and a density correction is needed to use data from a pressure transducer.

These researches above mainly focused on hyperconcentrated flow in the mountainous region with relatively steep slope. However, the sediment concentration of the lower Yellow River with a mild slope can reach above one thousand kg/m3, and the fine sediment particle content is also the highest in the world. When the sediment concentration reaches a certain threshold, the fluid characteristics of the muddy water and its sediment carrying capacities also change substantially. Such change makes it more efficient for sediment transport, and the deposition of the sediment on river bed can also be greatly reduced. Based on the field data analysis, this paper discusses efficient sediment transport mechanism of hyperconcentrated flow in the Yellow River.

Giant Dual Tunnels Completed Under Yellow River for South-to-North Water Transfer Project

A critically important tunnel beneath the Yellow River was completed recently for the construction of the central route of the giant South-to-North Water Transfer Project, which will supply thirsty cities and industries in the country’s northern cities.

Dubbed the “throat” of the central route, the 4250-meter-long, 7-meter-wide each (13,944-feet-long, 21-feet-wide) dual tunnels will help transfer 14.8 billion cubic meters (3.9 trillion gallons) of water a year from the tributary of Yangtze River Basin to the parched northern provinces of Hebei, as well as to the Tianjin and Beijing Municipalities by 2013.

The $US 97 million tunnel is the latest chapter in this landmark national infrastructure project — known as the South-to-North Water Transfer Project - which plans to eventually divert 44.8 billion cubic meters (11.8 trillion gallons) of water annually from the Yangtze through eastern, central, and western routes to relieve acute water shortages in northern China by 2050.

The water transfer idea was first conceived by former Chinese leader Zedong Mao in 1952, and was finally approved by the country’s Cabinet in December 2002, after debates that lasted nearly half a century. The mega-project, with an estimated total cost of $US 62 billion, has generated a strong current of public concern over land use, water pricing, possible regional climate changes, environmental damage, impact on agriculture, and massive human relocation.

Further reading about South-to-North Water Transfer Project, please visit: http://www.nsbd.gov.cn/zx/english/

Emptying Hengshan Reservoir to Flush the Sediment Out

Hengshan Reservoir is located in Shanxi Province in Northern China. It has multiple functions in water supply and flood control etc. It also has the first experimental double-curvature arch dam in China. This is a small reservoir on a steep stream. In the first eight years of operation, 24% of the reservoir capacity was occupied by sediment deposits. Flushing, which was undertaken with reservoir emptying in 1974, 1979, 1982 and 1986, was effective in restoring the lost storage capacity and indicated that flushing in every few years will be sufficient to maintain the long term reservoir use. 

In the 250 meters range in front of the dam, the sediment concentration of the flow was measured to be 1,200 kg/m3 and the total flushing time lasted 30 hours. The side slope developed by emptying the reservoir was 0.055. In the middle reach of the reservoir, the mud has very low water content, and it collapsed like Ichthyosis, even there are big chunk of mud floating on the water. In the upstream of the reservoir, the water content was even lower, the sediment deposition looked like crackings of a turtle. With the depth of the main channel being flushed to be higher, more and more mud from the side slope collapsed into the reservoir. 

Da Yu - The First River Engineer of the Yellow River

The Yellow River is the cradle of the Chinese civilization. She has fostered generations of Chinese but she has also brought troubles with her floods. The diligent Chinese people have been struggling to control the river for generations. Da Yu is considered to be the first real river engineer to control the flooding of the Yellow River.

Da Yu was born in the first dynasty of China called Xia Dynasty (夏朝) more than 4000 years ago. His father Gun (鲧) was also a river engineer, who was sentenced to death by the king Shun (舜) because of his failure to control the levee breach of the Yellow River. Da Yu inherited his father's experience, and after much investigation and research, he found the reason for the floods. He thought that the floods damaged the banks in the depressed floodplain areas because of the speed of the flow rushing from its high main channel. He led his fellow workers to dredge the main channel, and let the flow down to the lower area, then he successfully prevented the levee breach and river flooding.

Da Yu worked very hard on the river engineering issues of the Yellow River. He had been working in harnessing the river for 13 years. During these periods he did not go back his home, even 3 times when he passed by the front door of his house. This became a good example of how Chinese people are proud of. The legend about him is in reality a reflection of the ancient Chinese people who struggled against the floods of the Yellow River, but never obeyed their fate to surrender to the nature.

Because of his success in controlling the river,  Da Yu obtained the crown vacated by Shun according to the doctrine of handing the crown to the talented after abdication of the king. But it was Da Yu who passed his power to his own son Qi (启) by establishing the hereditary system. Then Qi founded the Xia Dynasty, the first Chinese dynasty recorded. The statue of Da Yu is being build at Huayuankou (lower reach) of the Yellow River. 

Hyperconcentrated Flow in Sanmenexia Reservoir of the Yellow River (1993) - Part I

After storing water and sediment for several months, Sanmenexia Reservoir in the middle reach of the Yellow River suddenly released water on June 25, 1993. Hyperconcentrated flow was created with a maximum flow discharge at 1,480 m3/s，and the sediment concentration was measured to be 300 kg/m3 for about 24 hours! The water surface elevation dropped from 307.5 m to 294.25 m in the reservoir. This video shows the channel created inside the reservoir by the hyperconcentrated flow.

History of the Yellow River

The Yellow River or Huang He is the second-longest river in China (after the Yangtze River) and the sixth-longest in the world at 5,464 kilometers(3,398 miles). Originating in the Bayankala Mountains in Qinghai Province in western China, it flows through nine provinces of China (Qinghai, Sichuan, Gansu, Ningxia, Inner Mongolia, Shaanxi, Shanxi, Henan,Shandong Provinces) and empties into the Bohai Sea. The Yellow River basin has an east-west extent of 1900 km (1,180 miles) and a north-south extent of 1100 km (684 miles). Total basin area is 752,443 km2 (290,520 mile2).

The headwaters of this mighty river lie in Kunlun Mountains in northwestern Qinghai Province. It runs through nine provinces and autonomous regions on its way to the Bohai Sea. It is not exaggerating to say that Yellow River is a melting port, because there are more than 30 branches and countless streams feeding it through its course. The vigorous upper reaches of the Yellow River starts in Qinghai Province to Hekouzhen in Inner Mongolia. This magnificent river flows quietly, like a shy girl in this section, irrigating the farmlands and nurturing the people. Its middle reaches ends at Taohuayu in Zhengzhou City, Henan Province. Here the Yellow River splits the Loess Plateau in half, forming the longest continuous gorge in the whole drainage area of the river. The Yellow River's lower reaches ends in a delta on the Bohai Sea.

It is agreed upon by almost all the Chinese people that the Yellow River is the cradle of Chinese civilization, the spiritual home of the Chinese people. It is the waters of the Yellow River and its spirit that nurture the whole Chinese nation. For thousands of years, the Yellow River has been admiring by literary giants, artists, as well as by the common people. The Yellow River is not just several letters, nor is it just the name of a yellow-ochre-colored river. It bears special significance: the symbol of the Chinese nation, the spirit of the Chinese people and more importantly, civilization itself.

Neolithic (7,000 BC-3,700 BC), Bronze (3,700 BC-2,700 BC) and Iron Age Sites (770 BC), and so on can be found in the Yellow River's drainage basin, which had been the center of ancient Chinese culture since the Azilian (Middle Stone Age). Here, the story of three cultural heroes: Suiren-shi who taught the Chinese to make fire by drilling wood, Fu Hsi who was the inventor of hunting, trapping and fishing and Shennong-shi who invented agriculture, was spread. It was these three legendary individuals that began the development of civilization in the Yellow River basin. After that, many ancient Chinese emperors, like Emperor Qin Shi Huang, Genghis khan (1162-1227, grandfather of Kublai Khan who is the first emperor of the Yuan Dynasty (1271-1368)) pushed the Yellow River civilization to a wholly new level of refinement, grace and spirituality which drew the attention of the whole world.

A Hyperconcentrated Flood Event of a Tributary of Yellow River (1994/09)

【Introduction】On September 1, 1994, there was a 50-year hyperconcentrated flood event of Beiluo River, tributary of Yellow River at its middle reach in northern China. Flow discharge is around 6,280 m3/s, sediment concentration is 690 kg/m3. Total sediment in 4 days of this event is almost 0.136 billion tons, and total water volume is 2.04 billion m3. This video shows the flood water passing through Daja County, Shannxi Province, China. The flood almost reached the roof of a building here.

Enjoy an Award-winning Song of "Life of the Yellow River"!

【Enjoy】A song "Life of the Yellow River", lyrics by Yiping Chao and the music by Xiaolu Wang. This is a song about keeping the healthy life of the Yellow River, and it has received many awards in China. You can also enjoy the beautiful scenery of the lower Yellow River.

【Lyrics in English】Pentium endless torrents, are your pounding pulse. Traveling through eternal time and space, are the green waves on both banks. Ah, Yellow River, my dear mother, coming along with grand songs, you cast a flow of history. Ah, take care of our mother river and dress her up, we will enjoy the sunshine and green with you together. Ah, love our mother river and repay her, we will sing the hymn of life with you together.

River course changing and levee breaching so many times, should not be your characteristics. River bed running dry again and again, is your silent whispers. Ah, Yellow River, my dear mother, keeping the healthy life of you, is our responsibility as your daughters and sons. Ah, take care of our mother river and dress her up, we will enjoy the sunshine and green with you together. Ah, love our mother river and repay her, we will sing the hymn of life with you together.